Added logic for working with Tarantool schema via Box

[KaymeKaydex]

• Implemented the box.Schema() method that returns a Schema object for schema-related operations

What has been done? Why? What problem is being solved?

I didn't forget about (remove if it is not applicable):

• [x] Tests (see documentation for a testing package)
• [x] Changelog (see documentation for changelog format)
• [x] Documentation (see documentation for documentation style guide)

Related issues:

[KaymeKaydex]

Please, add more unit-tests for a new requests/response. You could see how it is tested on the main package and inside the crud subpackage.

We also need examples (in example_test.go) with new features. This will help users to use the library.

Finally, we need to keep a backward compatibility until a next major release, so we need to add another Info() method with a context instead of changing the current one.

i removed interface changes added new examples for new methods and added more tests to make coverage up, now all methods are covered

[KaymeKaydex]

Please, fix the commit message:

box: ddded logic for working with Tarantool schema

Implemented the `box.Schema()` method that returns a `Schema`
object for schema-related operations

done

[KaymeKaydex]

@oleg-jukovec @DerekBum @themilchenko up

[oleg-jukovec]

Thank you for the PR! We've added some minor fixes and merged it: https://github.com/tarantool/go-tarantool/pull/446